1. FIELD OF THE INVENTION:
This invention relates to a dual thrust bearing for a shaft, and particularly, a thrust bearing for supporting a down hole well pump shaft.
2. DESCRIPTION OF THE PRIOR ART:
Down hole pumping units have long been employed in oil wells. Because of the diametrical constraints of the oil well casing, it has been the common practice in deep wells to provide a series of axially aligned pumping units mounted on and driven by a common shaft in order to generate sufficient pressure to effect the elevation of the well fluids to the surface. In any such pumping apparatus, a considerble axial thrust force is developed by each of the pumping units and, when a large number of such units are disposed in series, the resultant thrust load becomes larger than that which can be conveniently handled by a single thrust bearing, taking into account the diametrical constraints imposed by oil well casing.
It has therefore been necessary to insert a plurality of thrust bearings in spaced relationship along the length of a multi-unit pump. However, each such thrust bearing requires special mounting provisions relative to the pump housing and/or the well casing. Moreover, there is no assurance that the load imposed on each thrust bearing will be substantially equal because the tolerance variations that are inherent in a multi-unit string of pumps can result in an excessive load being imposed on a few of the bearings and a relatively light load on the remainder.